This invention relates to improved compositions such as medical and diagnostic compositions, and to methods of their preparation and use. The improved compositions are highly stable and have desirable physical and chemical properties.
By way of further background, therapeutic, diagnostic, and other similar compositions commonly contain materials which are naturally labile (i.e. sensitive to degradation, for example by oxidation or by the action of free radicals). This is unfortunate, since the labile materials are often the active or critical component of the composition, or otherwise lead to degradation products which render the composition unsuitable for use. As will be appreciated, labile materials can be any of a large variety of substances, including for example pharmaceuticals or biologic materials such as sugars, fats, oils, hormones, enzymes, cells or cell components, blood, blood fractions, etc. Quite naturally, therefore, there has been and is a continuing interest in developing new ways to stabilize these labile materials. Further, the means used to stabilize the labile materials, in the most optimum of circumstances, would also avoid, to the greatest extent possible, interference with or complication of the procedures involved in the preparation, storage, handling and use of the compositions including them.
As one specific example, enzymes, while enjoying a wide variety of analytic and therapeutic uses, are notoriously labile. For instance, enzymes are useful in various diagnostic tests, such as the in vitro determination of creatine, blood urea nitrogen (BUN), glucose, etc. To overcome problems related to lability, enzyme preparations are often lyophilized, or the enzymes are otherwise entrained in a solid matrix imparting stability. However, this not only can escalate the cost of the final product, but also often complicates handling and use of the product. As an example, lyophilized enzyme preparations must be reconstituted with water prior to use and preferably be used shortly thereafter. Significant delay in use after reconstitution can lead to an unreliable determination. Further, it is well known that enzymes, once lyophilized and then reconstituted, frequently suffer a loss of activity. This can render determinations unreliable even if the enzymes are used immediately after reconstitution. It is therefore desirable that laboratories performing diagnostic assays have available enzyme preparations which are stable over time yet can remain in liquid form.
Accordingly, over the years, there have been attempts to prepare stabilized liquid-form enzyme compositions for use in diagnostic procedures. For example, U.S. Pat. No. 4,310,625 to Modrovich discloses a liquid enzyme preparation stabilized by an organic solvent such as propanediol. The disclosed composition comprises an aqueous medium containing a lyophilized, dry enzyme, an organic solvent such as propanediol, a very small quantity of a polymer, such as polyvinylpyrrolidine or 0.1% gelatin, and, permissibly, from 1-18% of one or more salts plus a bacteriostatic agent. As disclosed in Modrovich '625, the organic solvent protects functional group sites on the enzyme molecule. U.S. Pat. No. 4,652,524 to Modrovich delineates another method of stabilizing enzymes. According to this method, the enzyme, in a liquid medium, is reacted with a polymer having certain pendant groups capable of covalently bonding with pendant groups on the enzyme. An ethylene-maleic anhydride copolymer is one specifically described for this purpose. The process employs small amounts of gelatin (0.225% typically), albumin, dextran, a substrate and sodium azide. These ingredients are mixed in solution and the resulting solution added to the polymer solution. This new solution is then added to a solution of the enzyme in a glycerol-water medium. Alternately, the enzyme solution can be added to the first solution prior to the addition of the polymer solution.
Despite these and other attempts to provide improved stable therapeutic, diagnostic and other similar liquid compositions including labile organic substrates such as enzymes, drugs, cells, etc., the commercial situation has remained essentially the same for many years. For example, very few, if any, liquid enzyme preparations have achieved significant success in the marketplace, and reports indicating unsatisfactory stability of other therapeutic and diagnostic materials have continued. It is thus apparent that there remains a need for improved stable liquid compositions in these areas and methods for their preparation and use. The applicant's invention addresses these needs.